A known collator feeds folded sheet material signatures onto a moving conveyor. The signatures are dropped from above the conveyor onto saddle bars on the conveyor which extend perpendicular to the direction of conveyor movement. The productivity of the collator is related to the speed of the conveyor and the spacing of the bars. The conveyor speed and the bar spacing are related to the time needed for the signatures to become positioned on the bars. An open signature which is dropped with its fold uppermost "parachutes", i.e., the inside surfaces of the signature encounter air resistance and movement of the signature is slowed, which increases the time needed for the signature to become positioned on a bar.